The present invention relates to a supra condylar intramedullary nail for the femur. More particularly it relates to an intramedullary nail using a novel condylus screw having two threaded nuts or two nuts having a ratchet system and a flexible washer mounted on the nuts.
In treating a femoral fracture, it is standard practice to use a fixation device adapted to facilitate recovery of the fractured bone. The fixation device provides immobilization of the bone fragments and stabilization of the fractured femur, thus providing earlier mobilization and weight bearing of a patient. The fixation device is attached to or inserted into the femur and cooperates with the bone fragments and the femoral shaft to stabilize the bone. As the bone heals, the fixation device allows the bone fragments to compress into each other so the fragments grow together to restore the bone.
Two prevalent types of femoral fractures are supracondylar or “T-type” condylar fractures about the distal femur. A number of different fixation devices, both external and implantable, have been devised for fixation of supracondylar and condylar fractures. In the past, treatment of condylar or supracondylar fractures consisted of stabilizing the bone portions with plates and screws. However, in using plates and screws, invasive surgery is required and includes considerable dissection of the thigh in order to expose the fracture so as to attach the plates and screws. The resultant devasculariztion of the distal portion of the femur has lead to a high frequency of complications of delayed union of the bone sections, osseous fracture and infection. Additionally, due to the muscular stresses in the region of the condylus and supracondylus, the treatment may involve undesirable post-operative procedures and complications including the bending or breaking of the plates, loosening of the screws and migration of the femoral shaft.
Intramedullary (IM) nailing has become a standard procedure for treating supracondylar and condylar fractures. In its basic form, IM nailing consists of driving a rod-like nail into the intramedullary bone canal of the femur to stabilize transverse fractures of the femur. To further stabilize the bone fragments interlocking cross-bolts or screws through the nail that are fixed on both sides of the fracture are used.
Known IM nails have been designed for treatment of condylar and supracondylar fractures. U.S. Pat. No. 6,010,505 Asche et al., the disclosure of which is herein incorporated by reference in its entirety, discloses an intramedullary device having an IM nail and interlocking bolts or screws to grip and stabilize the femoral condyles with respect to the femoral shaft.
In Femoral fractures involving the femoral condyles (e.g. T-condylar Fractures), an IM nail is currently used in combination with a Stryker Trauma T2 condyle screw (shown in FIG. 1A (prior art)) in order to realign, compress and fix the femoral condyle fracture fragments. The existing condyle screw system consists of one 5 mm diameter screw with a first pre-assembled 15 mm diameter washer at the level of the screw head (the washer position is fixed to the screw adjacent the head in a manner such that it is free to rotate in all directions). A second nut with a pre-assembled 15 mm diameter washer mounted thereon can threadably engage threads on the end of the screw opposite the head, (the washer position is fixed to the nut but, again, it is free to rotate in all directions).
In the prior art design once the screw is completely inserted into the bone medially, the nut is then screwed onto the screw laterally, a compression force will be generated between the washer and the bone cortex from both sides (lateral and medial). This compression force fixes the bone fragments. All the components (screw, nut, washers) are preferably made out of a titanium alloy, preferably grade 5. When the prior art condyle screw is used on an irregular-shaped-surface of the distal femoral condyles, the washers might not properly adapt to the cortical surface. As a result, the washer might protrude out the bone surface and impinge to the biological tissue. The impingement may involve the knee joint cartilage surface, generating pain, inflammation or even damage to the tibial plate cartilage. Furthermore the procedure to compress the fragments is time-consuming since many screw turns need to be carried out in order to achieve the contact of both washers (from both sides) to the bone cortex.